Conventionally, an apparatus configuration for forming parallel X-ray beams by arranging three slits is known as an apparatus for measuring X-ray small-angle scattering because of a need of irradiation of X-rays whose scattering angle is small in X-ray small-angle scattering measurement (Patent Document 1, Non-Patent Document 1). A slit is used to form thin beams, but when X-ray beams hit the end of the slit, parasitic scattering occurs and a tail is left in the scattering angle direction outside the generated beams. In the apparatus with three slits, parasitic scattering is removed by the second and third slits provided with a distance in between. However, in such an apparatus, it is necessary to provide a distance between the slits, and therefore, an apparatus with large dimensions is necessary.
On the other hand, the apparatus or the like is known that uses the Bonse-Hart method of detecting diffracted rays by a zero-dimensional detector while scanning a channel-cut monochromator crystal arranged on the beam-receiving side (Patent Documents 2 and 3, Non-Patent Document 2). FIG. 7 is a plan view showing an optical system that uses the conventional Bonse-Hart method. In the Bonse-Hart method, as shown in FIG. 7, a sample S0 is irradiated with X-rays generated by making X-rays reflected from the mirror enter a collimator 918 and the X-rays scattered by the sample are detected by reaching of the X-rays to an analyzer 919. In the apparatus configured by such an optical system, the scattered beams in the scattering angle direction are removed and thus measurement with a high resolution is made possible. However, it is not possible to simultaneously obtain anisotropic patterns by a one-dimensional detector or a two-dimensional detector.
In contrast to this, the apparatus described in Patent Document 1 cuts parasitic scattering of a pinhole collimator by the channel-cut monochromator crystal and performs detection with the two-dimensional detector. However, with such an apparatus, the nature of the X-ray to tend to diverge is left and the beams spread because the tail is not removed sufficiently. The reason is that the channel-cut monochromator crystals can be arranged only in arrangement of (+, −, +, −) and therefore, it is not possible to remove the tail caused by the spatial divergence.